Apparatus for introducing gas to hot metal in a bottom pour vessel

ABSTRACT

A sliding gate apparatus for controlling the pouring of hot metal from a bottom pour vessel into a continuous casting mold is disclosed. The gate includes a permeable refractory block positioned beneath the vessel pouring opening when the gate is in the active position. The permeable plug has a low permeability center, thus any gas introduced to the hot metal through the plug will tend to flow near the sides of the vessel opening.

United States Patent [191 Shapland [451 July 23, 1974 [75] Inventor:James T. Shapland, Wilkins Township, Allegheny County, Pa.

[73] Assignee: United States Steel Corporation,

Pittsburgh, Pa.

[22] Filed: Oct. 26, I973 21 Appl. No.: 409,834

[52] US. CI. 266/38 [51] Int. Cl. F2711 3/14 [58] Field of Search 266/34PP, 38; 164/66, j

' [56] References Cited UNITED STATES PATENTS 3,684,267 8/1972 Andllejtlkm 266/38 Primary Examiner-Gerald A. Dost Attorney, Agent, or FirmRalphH. Dougherty [57] ABSTRACT A sliding gate apparatus for controlling thepouring of hot metal from a bottom pour vessel into a continuous castingmold is disclosed. The gate includes a permeable -refractory blockpositioned beneath the vessel pouring opening when the gate is in theactive posi tion. The permeable plug has a low permeability center, thusany gas introduced to the hot metal through the plug will tend to flownear the sides of the vessel opening.

11 Claims, 7 Drawing Figures PATiNIEnJuLzamn' SHEET 1 0F 4 FIG.

38 6.4.5 SOURCE 3.825.241 saw anr 4 PAIENIED JULZ 3X9" FIG. 5

APPARATUS FOR INTRODUCING GAS TO HOT METAL IN A BOTTOM POUR VESSEL Thisinvention relates to an improved refractory closure apparatus throughwhich gas can be introduced to molten metal in a bottom pour vessel.

In the continuous casting of steel, molten metal is poured from a ladleinto an intermediate pouring vessel such as a tundish or a degassingvessel and from thence into a mold. The intermediate pouring vessel isusually recessed above the nozzle. The metal that first reaches thisrecess has already lost much of its heat to'the lining of the vessel.This rather quiescent metal settles into the recess, loses additionalheat to its surroundings and begins to solidify. The molten metal in thevessel above the recess does not contain sufficient superheat to remeltthe solidified metal. Opening the blocked recess has heretofore beenaccomplished by use of an oxygen lance or by use of slidable gates suchas are shown in U.S. Pat. No. 3,684,267. The use of an oxygen lance isundesirable as it impairs the quality of metal and usually damages thenozzle and refractories in the immediate vicinity of the nozzle. Whenthe slidable gate of FIG. 1 of U.S. Pat. No. 3,684,267 is used tointroduce gas to agitate the metal in thenozzle well, metal in thelowermost corners of the nozzle well against the slidable gate 16 failsto be agitated and thus freezes. Although the nozzle is opened, theinitial metal flow rate is generally slow and if the heat tends to becold, the stream can freeze before the opening is completely washedclean. If the slidable gates of either FIG. 2 or FIG. 3 of the patentare used to introduce inert gas to agitate the metal or to introduceoxidizing gas to burn the metal and create a superheated area to insuremetal flow, a situation similar to that of FIG. 1 of the patent isencountered. The permeability of the plug must be sufficiently high toprevent the entry of molten metal into the interstices of the plug andgenerally this high permeability causes the gas to flow unevenly throughthe plug. Additional gas is then channeled to the area where flow iseasiest. Thus gas is not introducedacross the entire area of the nozzlewell as intended. This results in a certain portion of the metal abovethe plug not being molten if the heat tends to be cold. The stream whichhas been constricted by thissolidified metal can freeze off before theopening is washed clean.

Since the area of the nozzle well that tends to be coldest is thatportion nearest the walls of the well, this is the region in which sculland-solidified metal is most likely to form. It is also the region fromwhich the scull is most difficult to wash free.

Slidable gates have been known since Lewis U.S. Pat. No. 311,902disclosed a reciprocable sliding gate in 1883. Shapland Reissue PatentRe. 27,237 discloses a slidable refractory closure member or gate forbottom pour vessels. Neither reference teaches a permeable plug in thegate through'which gas can be introduced to the molten metal in thevessel. Pol Detalle U.S. Pat. No. 3,581,948 teaches the use of apermeable plug 16 in an opening of a slidable gate for introducing gasto the nozzle well area. Each of his arrangements fails to disclose howto prevent solidification of material near the walls of his aperture 10.

It is the principal object of my invention to provide an improvedclosure apparatus which includes means for introducing gas through aslidable gate into the region in whichmolten metal is most likely tosolidify in a nozzle well of a bottom pour vessel.

It is also an object to provide a sliding gate closure apparatusequipped with means for either agitating hot metal or superheating hotmetal in the recess around the nozzle of a bottom pour vessel or both toinsure a smooth, free flowing stream when a teeming gate is placed inthe active position beneath the nozzle opening, replacing the inventedgate. 1 My invention is better understood with reference to thefollowing detailed description and the appended drawings in which:

FIG. 1 is a cross section through the nozzle of a bottom pour vesselequipped with a slidable gate constructed in accordance with myinvention.

FIG. 2 is a cross section of my invented sliding gate on a larger scalethan in FIG. 1.

FIG. 3 is a top view of the slidable gate of FIG. 2.

FIG. 4 is a cross section of an alternative sliding gate which employs apermeable refractory block having a number of holes therein.

FIG. 5 is a cross section of the gate of FIG. 4 taken along line V-V ofFIG. 4.

FIG. 6 is a cross section through the nozzle of a bottom pour vesselequipped with a slidable gate having an alternative gas supplyarrangement.

FIG. 7 is a cross section of an alternative sliding gate having anannular gas distribution chamber.

As shown in FIG. 1, bottom pour vessel 10 is provided with a refractorylining l2 for receiving molten metal. The bottom wall of the vessel hasa well or recess 14 and an outlet opening 16 and carries a nozzle plate17 fixed to its underside which plate 17 has a nozzle 18 aligned withthe opening 16. A sliding (or slidable) gate closure member 20 ismounted beneath the nozzle. The gate can be supported and operated inany desired manner, hence the supporting and operating mechanism is notshown. The gate includes a solid refractory portion 22 (see FIG. 2)having a central opening 24. A

high permeability (readily permeable) annular refractory ring or plug 26is situated in opening 24. The ring 26 surrounds a refractory core 28 ofa lower permeability (more dense) material or a nonpermeable material.Tofacilitate assembly of the slidable gate, there may be included abottom refractory 30. The sides and bottom of the slidable gate may becovered by a steel jacket 32. A pipe 34 communicates with chamber 36beneath ring 26 and is connected to a source of gas 38 (FIG. 1).

When vessel 10 is prepared to receive molten metal, gate 20 is placedinto the position shown in FIG. 1 and gas flow is started through thegate into the nozzle region of the vessel. Molten metal is then pouredinto the vessel. Gas fiow into the nozzle region prevents solidificationof metal in well 14, outlet 16 or nozzle 18 by agitating the metalnearthe nozzle wall to a greater degree than agitation of the metal inthe center of the nozzle well.

The alternative sliding gate configuration of FIGS. 4 and 5 includes apermeable refractory block 40 centered in the upper portion of the gate20. The block 40 contains a series of holes 42 near its perimeter tocreate a ring or zone of increased permeability. Thus most gas willfollow the path of least resistance and move upwardly through theportion of the permeable refractory block above these holes into thenozzle well in a ring of generally the same configuration as the holesbeneath it.

The alternative gas distribution system shown in FIG. 6 includes aslidable gate 60 which differs from gate of FIG. 1 only by theorientation of pipe 62. Pipe 62 communicates at one end with chamber 64beneath ring 66, and at the other end communicates with a mating pipe 68embedded in nozzle plate 17, which pipe 68 communicates in turn withpipe 70 which passes through vessel mounting plate 72 and is connectedto a source of gas 74.

The alternative slidable gate 80 of FIG. 7 includes an impermeable orlow permeability central core 82 (which can be cylindrical, ordual-cylindrically-shaped as shown) and a more permeable ring or sleeve84, so shaped to form an annular gas distribution chamber 86 in thegate. Pipe 88 communicates with chamber 86 and with gas source 74through pipes 68 and 70.

The advantage in having the gas pipes in the nozzle plate and mountingplate is that no time or effort is needed to attach a gas connection toa gas-injecting slidable gate. Positioning of the gate accuratelyeffects the necessary connection.

The gates of my invention perform in the same manner as a regularclosure gate in physically stopping the flow of molten metal yet theyperform the additional function of stirring or agitating the moltenmetal in the nozzle region thus preventing solidification of the metalin this region prior to the beginning of the pour. The gates have theadditional capability of performing as regular closure gates regardlessof whether a gas flow has begun. Should the permeable block becomeplugged or penetrated by molten metal, the gate can easily be replacedby a fresh gate.

It is readily apparent from the foregoing that I have invented aslidable gate for introducing gas therethrough to hot metal in a bottompour vessel which gas will agitate the metal near the walls of a nozzlewell to insure the nozzle opening upon teeming molten metal through thenozzle.

I claim:

1. A slide-through gate for closing the pouring nozzle of a molten-metalcontaining bottom-pour vessel, said gate comprising a first refractorybody,

a second refractory body set in said first refractory body and having anupper surface no higher than the upper surface of said first refractorybody, said second refractory body having an annular portion of higherpermeability than its center portion,

said refractory bodies forming a gas distribution chamber in said gate,and

means connected to said gate and communicating with said chamber forintroducing gas to said vessel through said second refractory body. 2. Agate according to claim 1 wherein said second refractory includes acentral refractory core of lower permeability than the surroundingportion of said second refractory.

3. A gate according to claim 2 wherein said central refractory core isnon-permeable.

4. A gate according to claim 1 wherein said second refractory has athick central portion and a thinner annular portion.

5. A gate according to claim 1 wherein said second refractory isprovided with a number of holes substantially normal to the uppersurface and extending from said chamber upwards into said secondrefractory to create a zone of increased permeability.

6. A gate according to claim 5 wherein said holes create a ring ofincreased permeability.

7. A gate according to claim 1 wherein said chamber is beneath saidsecond body.

8. A gate according to claim 1 wherein said chamber encircles a portionof said second body.

9. A gate according to claim 1 further comprising an impermeable metaljacket covering the sides of said gate.

10. A gate according to claim 9 further comprising an impermeable metaljacket covering the bottom of said gate.

11. In combination, a bottom pour vessel having an outlet in its bottomwall, a nozzle plate having a pouring nozzle therein fixed to saidvessel beneath said outlet and having said nozzle aligned with saidoutlet, and carrying a gas pipe in the body of said nozzle plateextending from the bottom surface of said nozzle plate to anothersurface of said nozzle plate, a slidable gate mounted beneath saidnozzle plate for closing said pouring nozzle; said gate comprising:

a first refractory body a second refractory body set in said firstrefractory body and having an upper surface no higher than the uppersurface of said first refractory body, said second refractory bodyhaving an annular portion of higher permeability than its centerportion,

said refractory bodies forming a gas distribution chamber in said gate,and

a gas pipe communicating with said chamber and extending to the uppersurface of said gate where it communicates with and is aligned with saidgas pipe in said nozzle plate; and

means communicating with said gas pipe in said nozzle plate forintroducing gas to said vessel through said gas pipes and said secondrefractory body.

1. A slide-through gate for closing the pouring nozzle of a molten-metalcontaining bottom-pour vessel, said gate comprising a first refractorybody, a second refractory body set in said first refractory body andhaving an upper surface no higher than the upper surface of said firstrefractory body, said second refractory body having an annular portionof higher permeability than its center portion, said refractory bodiesforming a gas distribution chamber in said gate, and means connected tosaid gate and communicating with said chamber for introducing gas tosaid vessel through said second refractory body.
 2. A gate according toclaim 1 wherein said second refractory includes a central refractorycore of lower permeability than the surrounding portion of said secondrefractory.
 3. A gate according to claim 2 wherein said centralrefractory core is non-permeable.
 4. A gate according to claim 1 whereinsaid second refractory has a thick central portion and a thinner annularportion.
 5. A gate according to claim 1 wherein said second refractoryis provided with a number of holes substantially normal to the uppersurface and extending from said chamber upwards into said secondrefractory to create a zone of increased permeability.
 6. A gateaccording to claim 5 wherein said holes create a ring of increasedpermeability.
 7. A gate according to claim 1 wherein said chamber isbeneath said second body.
 8. A gate according to claim 1 wherein saidchamber encircles a portion of said second body.
 9. A gate according toclaim 1 further comprising an impermeable metal jacket covering thesides of said gate.
 10. A gate according to claim 9 further comprisingan impermeable metal jacket covering the bottom of said gate.
 11. Incombination, a bottom pour vessel having an outlet in its bottom wall, anozzle plate having a pouring nozzle therein fixed to said vesselbeneath said outlet and having said nozzle aligned with said outlet, andcarrying a gas pipe in the body of said nozzle plate extending from thebottom surface of said nozzle plate to another surface of said nozzleplate, a slidable gate mounted beneath said nozzle plate for closingsaid pouring nozzle; said gate comprising: a fiRst refractory body asecond refractory body set in said first refractory body and having anupper surface no higher than the upper surface of said first refractorybody, said second refractory body having an annular portion of higherpermeability than its center portion, said refractory bodies forming agas distribution chamber in said gate, and a gas pipe communicating withsaid chamber and extending to the upper surface of said gate where itcommunicates with and is aligned with said gas pipe in said nozzleplate; and means communicating with said gas pipe in said nozzle platefor introducing gas to said vessel through said gas pipes and saidsecond refractory body.